221. What is database schema migration?
- a) Version-controlled changes to database structure
- b) Moving data between different database engines
- c) Converting NoSQL to relational schemas
- d) A backup rotation strategy
Answer: A - Schema migrations (managed by tools like Flyway or Liquibase) track incremental DDL changes.
222. What is the purpose of connection pooling?
- a) To reuse database connections and reduce overhead
- b) To combine multiple database connections
- c) To distribute queries across connections
- d) To encrypt database connections
Answer: A - Connection pools (e.g., HikariCP) maintain active connections for reuse rather than creating new ones per request.
223. Which of the following is NOT a database testing type?
- a) Unit testing
- b) Integration testing
- c) Regression testing
- d) Color testing
Answer: D - Database testing includes unit (stored procedures), integration (app+DB), and regression (schema changes).
224. What is data mesh architecture?
- a) A decentralized approach where domains own their data products
- b) A network of interconnected databases
- c) A type of graph database
- d) A physical data center layout
Answer: A - Data mesh treats data as a product with domain-oriented ownership and self-serve infrastructure.
225. What is the purpose of the SQL ROLLFORWARD command?
- a) To apply transaction log records during recovery
- b> To undo a database migration
- c> To advance a sequence generator
- d> To retry failed transactions
Answer: A - ROLLFORWARD reapplies committed transactions from logs after restoring a backup.
226. What is the difference between eager and lazy connection pooling?
- a) Eager creates connections at startup, lazy creates on demand
- b> Eager is faster, lazy is slower
- c> Eager works for OLTP, lazy for OLAP
- d> There is no difference
Answer: A - Eager pooling improves initial request performance but consumes more resources.
227. What is database observability?
- a) Monitoring metrics, logs, and traces to understand database behavior
- b> Making database schemas readable
- c> A type of database mirroring
- d> A backup verification technique
Answer: A - Observability goes beyond basic monitoring with correlated telemetry for root cause analysis.
228. What is the purpose of the SQL MIGRATE command?
- a) To apply schema changes from version control
- b> To move data between servers
- c> To upgrade database software
- d> To convert data types
Answer: A - Migration tools apply versioned SQL scripts to transition between schema states.
229. What is synthetic database testing?
- a) Generating artificial workloads that mimic production patterns
- b> Testing with fake data
- c> A type of unit testing
- d> Combining multiple test cases
Answer: A - Synthetic tests evaluate performance under controlled conditions before deployment.
230. What is the purpose of the SQL TEST_DATA_GENERATOR function?
- a) To create realistic sample data for development/testing
- b> To generate test queries
- c> To produce database benchmarks
- d> To validate data quality
Answer: A - Data generators (e.g., SQL Data Generator) create anonymized but statistically representative datasets.
231. What is database canary deployment?
- a) Rolling out schema changes to a small subset before full deployment
- b> A backup strategy using canary servers
- c> A type of database replication
- d> A security monitoring technique
Answer: A - Canary deployments reduce risk by testing changes on limited traffic before full rollout.
232. What is the purpose of the SQL EXPLAIN ANALYZE command?
- a) To show actual execution statistics for a query
- b> To explain database schemas
- c> To analyze storage utilization
- d> To validate SQL syntax
Answer: A - EXPLAIN ANALYZE executes the query and reports actual row counts and timings (unlike plain EXPLAIN).
233. What is database contract testing?
- a) Verifying that applications and databases meet agreed interfaces
- b> Testing database backup contracts
- c> A type of SLA monitoring
- d> Validating license agreements
Answer: A - Contract tests ensure schema changes don't break consuming applications.
234. What is the purpose of the SQL SCHEMA_DIFF function?
- a) To compare two database schemas and identify differences
- b> To differentiate data types
- c> To split schemas
- d> To validate schema design
Answer: A - Schema diff tools (e.g., in Liquibase) generate migration scripts between schema versions.
235. What is database performance baselining?
- a) Establishing normal performance metrics for comparison
- b> Setting minimum hardware requirements
- c> A type of indexing
- d> Configuring basic performance settings
Answer: A - Baselining captures query times, throughput, and resource usage under typical workloads.
236. What is the purpose of the SQL CONNECTION_POOL_STATS view?
- a) To monitor active/idle connections and wait times
- b> To pool statistical data
- c> To optimize connection strings
- d> To analyze network performance
Answer: A - Pool statistics help tune min/max connection settings and diagnose bottlenecks.
237. What is database chaos testing?
- a) Intentionally injecting failures to validate resilience
- b> Testing with random data
- c> A type of fuzzy testing
- d> A disorganized testing approach
Answer: A - Chaos engineering reveals how databases handle network partitions, node failures, etc.
238. What is the purpose of the SQL SCHEMA_SNAPSHOT function?
- a> To capture the current schema state for version control
- b> To backup schema definitions
- c> To create read-only schema copies
- d> To validate schema integrity
Answer: A - Snapshots enable declarative schema management by comparing desired vs actual states.
239. What is database performance regression testing?
- a> Ensuring schema changes don't degrade query performance
- b> Reverting to previous performance settings
- c> Testing database rollback speed
- d> A type of stress testing
Answer: A - Performance regression tests compare execution plans and timings across versions.
240. What is the purpose of the SQL CONNECTION_LEAK_DETECTOR?
- a> To identify unclosed database connections
- b> To find network leaks
- c> To detect memory leaks
- d> A security tool
Answer: A - Leak detectors track connection origins and lifespan to prevent pool exhaustion.